Question

Part 1-

A)

Design a circuit that utilizes one switch to turn on 2 motors and another switch to turn off both motors. Pressing and releasing PB1 will turn on motor 1 immediately and motor 2 after a 3 second delay. Pressing and releasing PB2 will turn off both motors.

B)

Next, design a circuit that utilizes 1 switch to turn on 3 motors. Pressing and releasing PB 1 will turn on motor 1 immediately; motor 2 will turn on 2 seconds after motor 1 and motor 3 will turn on 5 seconds after motor 1 but only if motor 1 and motor 2 are already running

Use 1 switch (press and release) to turn off motor 3 only and one switch (press and release) to turn off motor 1 and 2. If motor 1 or motor 2 turn off, motor 3 should also turn off.

Part 2-

For this part you will utilize 2 or more timers to create an adjustable duty cycle waveform that is on for 2 seconds and off for 3 seconds. Use a momentary (press and release) push button or toggle switch to enable (start) the waveform. You can use the EN or DN bit from one of your timers, tied to an output (OTE) to emulate the waveform output or you can create a simple latch circuit using a bit or OTE.

Answer 1

Part 1

A). On Pressing PB1 motor 1 (M1) turns ON immediately and the latching coil A picks up, which holds the NO contact A in closed position. At the same time the timer TON starts and after 3 sec delay, DN bit gets high which turns ON motor 2 (M2). As the latching coil is picked up, therefore even after releasing PB1 the motor and the timer TON will still run. On Pressing PB2 the latching coil A drops which opens the NO contact A, therefore the motor M1 and the timer TON stops and hence the motor M2 also stops at the same time.

Part 1

B). When PB1 is pressed motor M1 starts and the latching coil A is picked up which keeps the NO contact A in closed position. At the same time the timers TON1 and TON2 are started. Due to the closed contact A of the latching coil, the supply to the motor M1 and the timers TON1 and TON2 is ON. After 2 sec delay DN1 bit gets high which drives motor M2 ON.

Similarly, after 5 sec delay(from the time when M1 starts), DN2 bit gets high which drives motor M3 ON, provided DN1 is high( M1 and M2 are running).

Now when PB3 is pressed, latching coil B picks up, which opens the NC contact B before the timer TON2. So the TON2 stops and DN2 gets LOW. Therefore M3 STOPS.

Now if PB2 is pressed the supply to all the motors and timers get cut and all motors are turned OFF.

Part 2. When PB1 is pressed, the latching coil A picks up, which holds the NO contact A in the closed position, so that even after releasing PB1, the supply to the timers and the output is not cut.

As soon as PB1 is pressed, the timers TON1 and TON2 are started.

After 3 sec delay, DN1 gets high which Turns ON the O/P. The O/P is ON for 2 more seconds until DN2 gets high and resets both the timers TON1 and TON2. Now again for 3 seconds the O/P is OFF. As soon as the DN1 gets high after these 3 seconds the O/P again turns ON and after next 2 seconds it turns OFF again as the timers get reset again.

Hence the cycle repeats.